ABSTRACT The study of the influence of exercise on immune response is a field in constant grow since the 1970s. The main areas studied are infection of upper respiratory airways in athletes submitted to extenuating exercises, the exercise as a model of stress and the effects of training as an adaptive mechanism to cope with stress. Exercise promotes an imbalance in organic homeostasis, and all of the systems, including the immune system, must adequate their function to this new situation. The responses to exercise can be expressed as acute response, a transitory response to stress and chronic adaptive response, when training provides better conditions for the organism to cope with stress. In both situations the components of the immune system, the cellular and humoral arms of the innate and adaptive systems, are affected by exercise. Not as a rule, one can say that moderate exercise is associated with a better function of the immune system and high intensity exercise in stressful situations is associated with a transitory state of immunodepression.